Hot-air furnace



y 9 10. A. PETERS HOT AIR FURNACE Filed Dec. 30, 1941 3 Sheets-Sheet l @aq Q.

,eMaL

5 sheets-sheet 2 v I v 4 gnuo rvkoz (91150 Qazwak May 9, 1944. o. A. PETERS HOT AIR FURNACE Filed Dec. 50, 1941 a Sheets -She et s Wm (9am Q 72mm v NW mN Patented May 9, 1944 UNITED STATES FATENT OFFICE HOT-AIR FURNACE v Otto A. Peters, Toledo, Ohio Application December 30, 1941, Serial No. 424,913

2 Claims.

My invention relates to a hot-air heating system and, particularly, to a system that may be used to advantage for the heating of residences and other buildings.

As is well known, in systems of the character mentioned, heat is conveyed to the residence or building by the carrier air which has been heated by being brought into heat exchanging relation with a source of heat. The thermal output or delivered thermal units in such systems depends, considerably, upon the degree of thermal differential between the carrier air and the exchange surfaces of the walls surrounding the source of heat. Ordinarily, the source of heat is disposed in a fuel combustion chamber having a stack for conveying the gases and non-combustible products of com bustion, therefrom.

In the prior art, it has been the practice to extend a stack flue through a tortuous path, leading from the combustion chamber and traversing the stream of carrier air after the stream has passed from contact with the walls of the combustion space and to the systems supply side of the combustion chamber. This provision is alleged to enable said carrier air to receiv heat from the stack Walls heated by the gases and noncombustible products of combustion. I have observed that such is not the case, but that, by reason of the existence of a near thermal equilibrium or a thermal differential, unfavorable to thermally charging the carrier air and, in fact, operating to extract heat therefrom, the carrier air is deprived of heat and the heat of such gases and products of combustion, together with such heat as is extracted from the carrier air, is carried off and lost through the stack flue to the chimney. The above stated conclusion is substantially indicated by the stack or chimney temperatures which are prevalently high, sometimes to a dangerous degree, in the apparatus of the prior art.

My invention is based largely upon the foregoing observation and provides a furnace in which the gases and products of combustion are conveyed by stack ducts, having heat exchange surfaces, through the stream of carrier air approaching the walls of the combustion chamber and so that the differential between said stack duct surfaces and the carrier air is favorable to charging the air with said heat extracted from the combustion gases and by-products thereof. A furnace embodying the features of my invention experiences, in use, continuously low and safe stack temperatures, notwithstanding the intensity 'of demands made upon the furnace or the system of which the furnace is a part.

The invention has for an object to provide a building or residential hot-air furnace wherein the carrier air, conveying heat to the building or residence, may'extract greatly increased quantities of heat from the fuel and gases generated by the combustion thereof. Particularly, the invention has for an object to provide within a limited space, commensurate with that apportioned to furnace installations in buildings and homes, a means whereby the gases of fuel combustion are directed through chambers in which the carrier air, from the building or residence, moves to be charged with heat for subsequent exchange thereof with the interior of the residence building.

Another object of the invention is to provide, in a hot air furnace having a combustion chamber and a stack duct for conveying the combustion gases and by-products therefrom and to a chimney; a means for progressively directing carrier air into heat exchanging relation with duct and chamber surfaces, within the furnace, each of which surrounds a body of higher heat content than the air and each of which surrounds a body of higher heat content than the adjacent surface just previous in heat exchanging relation with said air. A still further object is to provide, in a furnace having the above described elements, a means arranged and constructed to direct the carrier air into heat exchanging relation with a surface of a chamber or duct body having, at each instance of establishment of said exchanging relation, a temperature in excess of the temperature of the carrier air during the entire period of ari travel, from the return plenum to the supply plenum of the furnace, through the furnace. A still further object of the invention is to provide, in a furnace having the above described elements, a means for directing the returning carrier air in heat exchanging relation with the cooler surfaces of the stack duct, and progressively therefrom to the warmer surfaces of said duct and of said chamber, whereby the air may extract substantially all heat from said combustion gases and by-products conveyed by said duct.

A further object of my invention is to provide, a system wherein the gases of combustion are directed through gas conducting and heat exchanging means so disposed and arranged as to cause precipitation of the fly ash or other noncombustible elements of said gases therefrom and on to surfaces of minor area, as compared to the heat exchange areas of said system. By such provision and arrangement, th precipitation of fly ash and other non-combustibles is restricted to surfaces having little or no heat exchange capa bility and is prevented from occurring to deposit said fly ash on heat exchange surfaces, which materially contributes to the eificiency of the system. By such provision and arrangement, the problem of gradually reduced efficiency of domestic furnaces experienced by users of prior art furnaces, due to deposition of gradually increasing and thermally insulating quantities of fly ash and other non-ccmbustibles on heat exchange surfaces thereof, is solved. The efiiciency of a furnace embodying my invention is, therefore, reasonably constant, notwithstanchng its continued use, without cleaning.

A particular object of the invention is to provide, a furnace having a plurality of inter-communicating chambers, disposed in tandem relation between the return plenum and the supply plenum of the system of which the furnace is a part, the fire pot of the furnace being located in the chamber most proximate to the supply plenum of the system and the fiue stacks extending through each successive chamber intermediate the fire pot containing chamber and the return plenum. It is apparent that the chambers form zones of heat exchange with said air of gradually increasing intensity in degree, as the fire pot containing chamber is approached by said air. It will also be apparent that the temperature in said zones will always be higher than the temperature of the carrier air directed therein, and that a thermal differential favorable to charging the air with heat is maintained in each successive zone until the air is discharged to the supply plenum.

The invention consists in other features and advantages which will appear from the following description and upon examination of the drawings. Structures containing the invention may partake of different forms and still embody the invention. To illustrate a practical application of the invention, I have selected a hot-air furnace as an example of the various structures and details thereof that contain the invention and shall describe the selected structure hereinafter, it being understood that variations may be made without departing from the spirit of the invention. The particular structure selected is shown in the accompanying drawings and described hereinafter.

Fig. 1 of the accompanying drawings illustrates a perspective view of the furnace selected to illustrate an embodiment of my invention, certain of the interior parts therein contained, being shown in broken lines. Fig. 2 illustrates a perspective view of a fabricated unit of parts within said furnace. Fig. 3 illustrates an enlarged View of a longitudinal sectional elevation of the furnace shown in Fig. 1, having the unit shown in Fig. 2, therein. Fig. 4 illustrates a view of a section taken along the plane of line 4-4 indicated in Fig. 3.

The embodiment of my invention in the hot air furnace illustrated in the accompanying drawings has a main housing shell I comprising a plurality of vertically extending panels 2, interjoined at their approximating edges by vertically extending panels 3. The lower end of the shell may be closed in any suitable manner, as by the surface 4 of the floor on which the lower edges of the panels 2 and 3 rest. If desired, suitable angle shoes 5 may be secured along the joint of said panels 2 and said base. The upper end of the hell I is preferably closed by a top panel 1 which may be secured to the upper edges of the panels 2 and 3 in any suitable manner.

The top panel 1 has two openings 8 and 9, disposed in spaced relation to each other. the opening 8 being most proximate to one end of the panel 1 and the opening 9 being most proximate to the other end. Superimposed on the panel 1 are walls I0 which define a plenum chamber II in direct communication with the opening 8. Also superimposed on the panel 1 are walls I2 which define a bonnet or second plenum chamber I4 in direct communication with the opening 9.

If desired, the shell may be thermally insulated by the provision of walls I5 disposed in lapped insulating relation to certain of the panels 2 and 3 designed to be in proximity to the sources of greatest heat generation Within the furnace. The walls I5 serve, not only in an insulating capacity but also, to define, in conjunction with other parts to be hereinafter described, certain advantageous chambers or zones for the passage of air.

Said chambers or zones are sequentially arranged in tandem relation, extending from the opening 8 to the opening 9. The chamber I8 is in direct communication within the plenum chamber II and is defined within the shell I by a wall I9 suspended from the top panel 1 and having an extension 2 I adjoining the lower portion of a vertically extending wall 24. Disposed in the chamber I8 is a suitable air propelling means, such as the motor driven sirocco fan 20. The chamber I2 communicates with a next successive chamber 22, through an opening 23 in the extension wall 2|, as modified by the action of the fan 20.

The chamber 22 is defined within the shell I, not only by said wall I 9 and its extension 2 I, but also by the upper portions of the wall 24. The upper edge of the wall 24 terminates along a line spaced from the top panel 1. The chamber 22 communicates with a next successive chamber 25 through the space between the upper edge of the wall 24 and the top panel 1.

The chamber 25 is defined within shell I by the wall 24, portions of the insulating walls I5 and a depending wall 21. The depending wall 21 extends from the top panel 1 to a line spaced from the surface 4 along which the lower edge of the wall 21 extends. The chamber 25 communicates with a next successive chamber 28 through the space between the lower edge of the wall 21 and the floor surface 4.

The chamber 28 is defined within the shell I by portions of the walls I5 and the wall 21. The chamber 28 is in direct communication with the bonnet or plenum chamber I4. The plenum I4 may be connected to suitable supply ducts, not shown, and the plenum II be connected to suitable return ducts, not shown. Thus, the carrier air, in response to the operation of the fan 20 and the pressures created thereby, is caused to move in a stream, generally indicated by the arrows a shown in Fig. 3 of the drawings, from the return plenum II and progressively through the chamber I8, the chamber 22, the chamber '25 and the chamber 28 to the supply plenum l4.

Disposed within the chamber 28 is the combustion drum 3!) in which is located 'a suitable fire pot 3| for supporting the fuel during combustion thereof. It will thus be apparent that during the time the carrier air is directed into the chamber 28, and from there, enters the supply plenum I4, the carrier air is in heat exchanging relation with the walls of the combustion drum 30 which are highly heated by the combustion of the fuel therein. At this time, the thermal differential between the carrier air entering from the return plenum II and combustion drum surfaces is of great magnitude resulting in considerable heat exchange from the drum wall surfaces to the air. The carrier air, thus highly charged with heat, is directly sent to its function by way of the supply plenum M.

In order to efficiently utilize the heat of gases and other by-products of combustion produced Within the drum 30, flue means is provided extending from said drum 3!] and progressively,

and.successively through and from chamber 28,

through chamber 25, chamber 22 and chamber Hi to be discharged through a chimney, not shown. Thus, as the carrier air moves through the chambers, the air is successively and progressively brought in heat exchanging relation, through the medium of said line means, with the combustion gasesand by-products having, in each chamber, a progressively higher temperature. The results of this arrangement are that the thermal differential between the air and said flue means constantly increases and heat flows readily to the carrier air from the said gases and by-products. Finally, the temperature of said gases and byproducts as they move in said fiue means from the chamber I8 are greatly reduced, resulting in low and safe stack temperatures.

In the structure illustrated in the accompanying drawings, said flue means is embodied in various ducts extending from the drum 30 to the exterior of the shell I. Preferably, an opening 35 is formed in the drum 3%, proximate to the upper end thereof, which communicates with a header 36, disposed in chamber 28. The gases and by-products of combustion are received from the drum 3|) into the header 36 where the stream of gases is divided and conveyed through a pair of ducts 3'!v communicating directly with said headen The ducts 31 extend downwardly through the chamber 28 and have substantially parallel and vertically extending major longitudinal axes. The ducts 31 communicate direct ly with a box 39 disposed below the lower edge of the wall 21 and extending on either side thereof into the lower ends of each of the chambers 28 and 25. Thus, portions of the bottom of the box 39 are located in vertical alignment with said ducts 31.

By reason of the division of the stream of gases and by-products of combustion occurring in the ducts 31, the speed of movement of said gases is materially reduced permitting an opportunity for the fly ash content of said gases to precipitate and deposit on the bottom of the box 39. Access to within the box 39 may be had through a suit able opening in the box 39 and shell I which may be closed, at other than required times for removal of accumulated ash in said box, by a door 40, The streams of gases received from the ducts in said box 39 are again divided and di rected through a plurality of ducts 4|, greater in number, but lesser in cross sectional area than the ducts 31.

The ducts 4| extend, from the top of the box 39, upwardly through the chamber 25 and, preferably, so that the major longitudinal axis of each extends substantially vertical and parallel to the corresponding axis of the other of the ducts 4|. Thus, should there still be any unprecipitated fly ash in the gas conveyed by the ducts 4|, the same will fall to the floor of the box 39. The partition of the combustion gas stream which is effected as the gas is discharged from the box 39 through the ducts 4| assures that large quantities of heat will be extracted from the gases and absorbed by the carrier air passing through the chamber 25. This result is accomplished by reason of the increased surface area presented by said ducts 4| for heat exchange and also by reason of the extensive intimate contact with the inner surfaces of the walls of said ducts 4| to which substantially every portion of the combustion gases is exposed, and the likewise extensive intimate contact with the outer surfaces of the duct walls to which substantially all portions or the carrier air is subjected.

If desired, in order to enforce even more intimate contact of the carrier air with the outer surfaces of the ducts 4| suitable baflles 42 may be disposed in vertically spaced relation within the chamber 25. The baffles 42 cause the carrier air to move in a labyrinthian path, traversing the outer surfaces of the ducts 4| many times before completing its passage through the chamber 25. Further, if desired, the plurality of ducts 4| may be increased to a number greater than those shown in the accompanying drawings. Thus, the air moving through chamber 25 extracts much of the heat contained in the gases of combustion passing through the ducts 4|. The gases of combustion are received from the ducts 4| into a second header 44.

The header 44 is located near the upper end of the chamber 25 and communicates with a cylindrical stack flue 46, The stack flue 45 extends through the chamber 22 and has an extension 41 which extends through the chamber l8 and is adapted to communicate with a chimney, not shown, to convey the spent gases to the exterior.

Preferably, the header 36, ducts 31, box 39, ducts 4|, header 44 and stack flue are fabricated into a single unit such as shown in Fig. 2 of the accompanying drawings. When so fabricated, the various parts may be more easily handled for shipping and installation than when handled in separate parts and also may be more securely sealed. against escape of gases conveyed therethrough.

Thus, the gases of combustion move from the combustion drum 3U progressively through the ducts, headers and box in a stream and streams as indicated by the arrows g, shown in Fig. 3 of the accompanying drawings, until they are discharged to the exterior. During said movement, the carrier air, which is being moved always in counter direction to the direction of gas movement, extracts much of the heat therefrom with the result that not only does the furnace operate efficiently, but also that the stack temperature is maintained at a low and safe degree. Also, by reason of the novel means provided for precipitating the fly ash, the efiiciency of the furnace is reasonably constant over long periods of time, notwithstanding the failure to clean the same.

While in accordance with the provisions of the statutes, I have illustrated and described the best forms of my invention now known to me, those skilled in the art will readily understand that many changes may be made in the forms of construction disclosed, without departing from the spirit of my invention as set forth in the appended claims.

I claim:

1. In a hot-air furnace having a plurality of air confining, intercommunicating and sequentially adjoining chambers the endmost one of which has an opening to receive air from the exterior of the furnace and the other endmost chamber containing the source of heat and having an opening to discharge air to the exterior of the furnace, said source of heat comprising a combustion drum in which fuel may be ignited and burned, the combination therewith of a heat conductive, integrated shell, the shell having certain walls defining a laterally extending header, the interior of which communicates with the interior of the combustion drum, other wails depending from said laterally extending header and defining a pair of parallel ducts communicating with said header, other walls extending substantially at right angles to the duct walls to form a box communicating with said ducts, other walls extending vertically and parallel to said ducts to form a plurality of vertically extending, parallel passageways communicating with said box and of a number greater than the number of aforesaid ducts, other walls extending at right angles to the passageway walls defining a manifold cornmunicating with the aforesaid passageways, and other walls defining a tail pipe communicating with the aforesaid manifold whereby the products of combustion from the aforesaid drum pass successively through the aforesaid header, ducts. box, passageways, manifold and tail pipe; the ducts being spaced with respect to the passageways to dispose the ducts in one of said chambers proximate to said drum and dispose the passageways in another chamber more remote from said drum, whereby the air moving through said chambers is progressively heated by contact with said passageways and ducts heated by the products of combustion passing therethrough.

2. In a hot-air furnace having a plurality of air confining, intercommunicating and sequentially adjoining chambers the endmost one of which has an opening to receive air from the exterior of the furnace and the other endmost chamber containing the source of heat and having an opening to discharge air to the exterior of the furnace, said source of heat comprising a combustion drum in which fuel may be ignited and burned, the combination therewith of a heat conductive, integrated shell, the shell having certain walls defining a laterally extending header, the interior of which communicates with the interior of the combustion drum, other walls depending from said laterally extending header and defining a pair of parallel ducts communicating with said header, other walls extending substantially at right angles to the duct walls to form a box communicating with said ducts, other walls extending vertically and parallel to said ducts to form a plurality of vertically extending, parallel passageways communicating with said box and of a number greater than the number of aforesaid ducts, other walls extending at right angles to the passageway walls defining a manifold communicating with the aforesaid passageways and other walls defining a tail pipe communicating with the aforesaid manifold whereby the products of combustion from the aforesaid drum pass successively through the aforesaid header, ducts, box, passageways, manifold and tail pipe; the ducts being spaced with respect to the passageways to dispose the ducts in one of said chambers proximate to said drum and. dispose the passageways in another chamber more remote from said drum, whereb the air moving through said chambers is progressively heated by contact with said passageways and ducts heated by the products of combustion passing therethrough; and said box having an opening aligned with the several points of communication of said passageways with said box through which prodnets of combustion condensed in said passageways and falling therethrough may be removed from said box.

OTTO A. PETERS. 

